(1) Field of the Invention
The present invention relates in general to a door locking system of a motor vehicle, and more particularly to a so-called "magnetic door locking system" which can lock the door from outside by only bringing a magnet piece close to a magnetic sensor mounted in the door.
(2) Description of the Prior Art
Nowadays, in order to facilitate door locking from outside, a magnetic door locking system has been proposed in a motor vehicle, which comprises generally a magnetic sensor mounted in the door, control means for locking the door when the sensor senses a predetermined magnitude of magnetic force applied thereto, and a magnet piece carried by the car owner (or driver). Upon requirement of door locking from outside, he or she brings the magnet piece close to a given portion of the door where the sensor is positioned. With this handling, the sensor actuates the control means to lock the door.
In the system mentioned as above, for improved portability of the magnet piece and easier handling of the same, it has been also proposed that the magnet piece is combined with a door locking key (that is, an ignition key) which is engageable with a door-mounted key cylinder to lock or unlock the door and the magnetic sensor is conveniently positioned in the vicinity of the key cylinder. However, in this close or convenient arrangement, it sometimes happens that the door unlocking operation by the key from outside would induce re-locking of the door because of the magnet piece which issues magnetism to the near-positioned magnetic sensor. This is quite inconvenient when opening of the door is actually required. This drawback will be described in detail hereinafter.